[JAVA][Exception] Map Duplicate key

Exception 내용

Duplicate key 001 (attempted merging values sample.cafekiosk.spring.domain.product.Product@6b5fdbd0 and sample.cafekiosk.spring.domain.product.Product@2100b770)
java.lang.IllegalStateException: Duplicate key 001 (attempted merging values sample.cafekiosk.spring.domain.product.Product@6b5fdbd0 and sample.cafekiosk.spring.domain.product.Product@2100b770)
	at java.base/java.util.stream.Collectors.duplicateKeyException(Collectors.java:135)
	at java.base/java.util.stream.Collectors.lambda$uniqKeysMapAccumulator$1(Collectors.java:182)
	at java.base/java.util.stream.ReduceOps$3ReducingSink.accept(ReduceOps.java:169)
	at java.base/java.util.ArrayList$ArrayListSpliterator.forEachRemaining(ArrayList.java:1625)
	at java.base/java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:509)
	at java.base/java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:499)
	at java.base/java.util.stream.ReduceOps$ReduceOp.evaluateSequential(ReduceOps.java:921)
	at java.base/java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
	at java.base/java.util.stream.ReferencePipeline.collect(ReferencePipeline.java:682)
	at sample.cafekiosk.spring.api.service.order.OrderService.findProductsBy(OrderService.java:36)
	at sample.cafekiosk.spring.api.service.order.OrderService.createOrder(OrderService.java:26)
	at sample.cafekiosk.spring.api.service.order.OrderServiceTest.createOrder(OrderServiceTest.java:65)
	at java.base/java.lang.reflect.Method.invoke(Method.java:568)
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1511)
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1511)

 

문제가 된 부분

List<Product> products = productRepository.findAllByProductNumberIn(productNumbers);
    Map<String, Product> productMap = products.stream()
        .collect(Collectors.toMap(Product::getProductNumber, p -> p));

productRepository.findAllByProductNumberIn의 결과를 Map으로 바꿔주는 과정에서 발생한 에러다.

결과인 products에서 key를 Product::getProductNumber로 value를 Product로 변환해주는 과정에서 key값이 중복이 될 때 발생한 문제다.

 

key가 중복이 되는지를 체크하는 것이 필요하다!